Enclosed track speargun

I can't see it being anything more than two 5/8 bands.

For this gun, yes. But I think the same track might work well for a hybrid with a little more power. This just strikes me as the kind of thing with potential beyond the oringinally conceived application.

Quote from hau

sdeisen---IMO, I think that many here would agree that the worst case REAL LIFE senareo for an enclosed track gun is when the shaft is fired and the shaft hits something solid before the shaft TOTALLY exits the enclosed track. IMO, this is when the enclosed track is stressed the most and when most enclosed tracks tear out. What that means to me with this 120cm ETPGB is that I cannot shoot the ETPG towards any hard coral back stop LESS than 40in from the end of this gun without concern for the safety of the ET.

i dont think i ever really do that anyway,, maybe under ledges and stuff.. but i think itd be an easy enough thing to remember

Quote from hau

Don Paul--Personally I am going to continue using the same (2) 9/16 bands that I currently use with my RA 120cm rail barrel for this 120cm ET barrel. IMO, it is very easy to overpower a pipe gun and adding power is NOT one of my reasons for designing this ETPGB.

What is your reason then?

Quote from hau

Another item to consider is that this ETPGB is going to be HEAVIER than almost any RAIL barrel.
1. Good==because the felt recoil, barrel flex and muzzle flip will be decreased with the added barrel weight.

Why does this matter if with two 9/16 bands you have no significant recoil, barrel flex, and muzzle flip?

Quote from hau

I prefer a pipe gun for lots of reasons and would prefer an enclosed track pipe gun for many more reasons. But it is just my humble preference.
For me, an enclosed track pipe gun would:
1. Faster to reload. Many times I have to load my spear shaft fast without taking my eyes off a fish or spot below. It is easier to just start the shaft into the end of the enclosed track barrel and slide it into the mech.

I agree and IMO it's the only valid reason in this situation. Although some people will argue to the contrary and say that an enclosed track is slower to load. You should ask Jeff to open up the track a few inches near the muzzle and taper it for further ease of loading.

Quote from hau

3. Protect my spear shaft from injury while the shaft is in the gun. Less scratches and dings to the spear shaft "enclosed" in the CF

Sorry hau there's just no other way to say it, that's ridiculous. Get rid of that POS rusting Rob Allen shaft and get yourself a stainless steel one. Really you have no choice in the matter because as far as I know RA doesn't make euro shafts with full size sharkfin tabs, which you must have if you're going to use an enclosed track.

Quote from hau

5. An enclosed track pipe gun would be very fast and easy to freeshaft with

But neither you nor anyone else here freeshafts. Freeshafting is fundamentally for scuba divers and scuba divers don't like to chest load as you must do with a Rob Allen speargun. They use hip loading wood guns.

Regardless I'm glad you got your wish, congratz and enjoy your new toy.

I don't at this time. I have shafts with mini tabs like pictured below but not full size tabs which is what you need. I am working on getting a source for the full size tab shafts.

Quote from hau

Don Paul--Personally I am going to continue using the same (2) 9/16 bands that I currently use with my RA 120cm rail barrel for this 120cm ET barrel. IMO, it is very easy to overpower a pipe gun and adding power is NOT one of my reasons for designing this ETPGB.

Another item to consider is that this ETPGB is going to be HEAVIER than almost any RAIL barrel.
1. Good==because the felt recoil, barrel flex and muzzle flip will be decreased with the added barrel weight.
2. Bad===because the ETPG MAY not float enough for some spearos in some applications. (Like me with a reel AND UW cam).

Thanks hau, 2- 9/16 at 300% elongation will not over power a 7mm shaft of 17/4 ph shaft with fixed flopper.
You will need slightly more power as your shaft will be dragging a bit of water behind the tail, this will be dependent of track slot width and any boat tailing applied to the shaft.

Cheers, Don

Boat tailing? Is this slight tapering of the back end of the shaft, the same that makes it a little smoother for the shaft to engage in the mech?

"Boat Tail", as in the back end of a bullet, is usually a little more elongated than the short chamfered edge that you referred to Dan.

Here's a reworked shaft.

One more.

Does tapering the ends of the power bands have a beneficial hydrodynamic effect then? It's a much larger area than the end of the shaft, multiplied by several bands. But only over the band stretch length, and not the entire shot distance.

Quote from Tin Man

Does tapering the ends of the power bands have a beneficial hydrodynamic effect then? It's a much larger area than the end of the shaft, multiplied by several bands. But only over the band stretch length, and not the entire shot distance.

Yes, salt water is almost 900 times denser than air, I used to shoot threaded articulated wishbones
in the late 70's with one 17mm band. I found that after I ditched the ''sea ancors'' and ground long tapers
on my band the speed on my test gun shaft increased by 2 meters per second. 50MPH is 22.35 Meters
per second FWIW. Some Italian gun builders scratch their heads at the bundles of poorly constructed
power bands and thick rope wishbone some sell. Here in the US we sometimes keep adding HP rather then
design the car body to have less drag. Same with our guns.
Cheers, Don